I'd be interested in hearing strava engineers perspective also. Similar to your guess, my guess would also be that its an accuracy issue. There are some pretty big differences between various GPS tracking devices, and I suspect the margin for SOME users is much worse than a couple of % when looking at such a short segment. Say the fastest time is 30 seconds on a 300m segment (22.36MPH). Depending on a GPS ping here and a GPS ping there... I think some riders will see 5-10 seconds of variation which would render the segment pretty difficult to fairly measure. That's probably an exaggerated example, but that's my guess. My other guess is that they had to draw to line somewhere to prevent the segment database from getting overrun with tiny segments, or drowning out more "important" segments. 

As I'm sure you are aware, Strava bike Segments are numbered sequentially in the order they were created.  I started using Strava in 2017 and the first Segment I created had a number around 17,000,000.  At that time it was clear (from trial and error) that the minimum Segment length was 300m.  The latest Segments are numbered around 32,500,000.  I have completed quite a few Segments that are shorter than 300m and the highest Segment number of these is around 14,000,000.  Hence I infer that Strava set a minimum length of 300m in about 2016.  This seems perfectly reasonable - I have completed Segments that pre-date this change that are as short as 45m (the KOM is 6 seconds !) and these are clearly not suitable for meaningful competition.  

I agree that a minimum Segment length is appropriate - I'm just curious that after it being 300m for about 6 years why has it been decided to raise the limit to 500m ?  I've heard that some GPS systems only record every 5 seconds but, despite looking at many Strava Activities, I don't think I've seen an Activity with such large step intervals (by counting the data points in my Activities it seems my own GPS interval is about 1 second, despite it being from a very old phone).

The number of Strava users and Segments is no doubt increasing and so there is ever more data to be handled by Strava - however, the cost of data analysis and storage continues to fall so I doubt this would be a reason for the change. 

Strava could improve accuracy of segment timing (quite significantly) without raising the minimum segment length by implementing interpolation of segment timestamps. Even when someone uses smart recording and has recorded points further apart it is hard to imagine that person changing the speed drastically within a few seconds, so interpolation could help to determine more precisely when they went by the segment start or finish. Also, a smaller radius could be used for the interpolated points (once the initial match is found) which would help to prevent falsely matching a segment when someone didn't actually cross a segment start or finish. With the current implementation there are a lot of opportunities to cheat or misuse segments. For example, one can simply turn around 30-50 meters before the segment end, and that segment would still match and that person could cut 10+ seconds if they are running. Perhaps it isn't easy to turn around on a bike but very easy when running, and I see that happening a lot on uphill segments.

By the way, I don't know if the same 500m limit applies to running segments. If that is the case that would really hurt uphill segments and stairs. There aren't that many steep hills that are longer than 500 meters.

What Strava does with increasing the limit has nothing to do with improving the absolute accuracy of segment matching. That merely reduces the relative error which makes the timing errors less noticeable.

If Strava engineers are interested, I could suggest an interpolation algorithm that wouldn't significantly increase the computing cost of matching segments.

I've been prompted by Strava to identify 1 of the first 3 replies as an "accepted solution", however, I'd prefer to wait until my question has been answered and I'm still hoping to get some feedback from Strava about the reasons for their changes (which don't seem to have been led by customer requests) 

I have contacted strava support on this and they told to bring it here so community would get more visibility on this.

I too had estimated the limits to be rised from 300m into 500m and support confirmed:
We have a limit in place to make sure that newly created segments would result in more accurate leaderboards and reduce segment noise overall. There are minimum distance requirements for ride segments (500m) as well as other sport types (250m).

So 500m for all cycling, 250m for running.

As I see, the shorter mtb segments would usually be in local forrest, where it is really difficult to get the 500m or it would be making dangerous segments if you need to cross a road or walkway to get to the 500m.

Also the speeds in such places are a lot less than on the road, so there would be more gps points recorded than on road segments that also are 500m limit.

So it would be really nice to get back the 300m (or even 250m) limit.

For the segment noise part, it would be also nice to be able to flag runs that clearly are not following the segment.

The new minimum segment length of 500 is especially silly when it comes to virtual segments (on platforms like Zwift, for example). On those segments, GPS is recorded consistently - Zwift records every 1s, for example. So shorter segments should be allowed, since accuracy is ensured across all users.

I wrote a thorough post about this on Zwift Insider which explains several reasons why Strava's current minimum length requirement is silly in the context of Zwift. I do hope Strava will reconsider.

https://zwiftinsider.com/strava-minimum-segment-length/

There needs to be some consideration for the time it takes to complete the segment instead of just length.  A road bike may be able to do a 500m segment in 40 seconds or so.   Whereas a 250m mountain biking segment could easily take over a 60 seconds to complete, depending on terrain.  

My suggestion is people can "submit" a segment for approval, and if let's say 50 different riders have ridden it and the top 10% avg time is greater than 45 seconds, then it should be legit.  

I just threw some numbers out there.  Strava has access to all of the data, so you can compute would looks like a legit segment for mountain bikers, before it gets approved.

There are too many mountain bike trails less than 500m -- Strava needs to figure this out. 

Super disappointed with Strava on this one. We have lots of very steep gravel climbs in Western PA that are less than 500 meters long. Too many were already eliminated for segment creation by the last arbitrary and unrequested longer segment requirement. I also don't believe the real reason for this change is that shorter segments are too hard to time accurately. How does determining when a start and finish line are crossed get easier if the start and finish lines are closer together?

I notice that in my local area a significant proportion of the new Segments created in the last few months have a length of 0.31 miles, the current minimum allowed by Strava. This suggests that Segment creators have been constrained by the somewhat arbitrary limitations and would probably have preferred to have their Segments a little shorter. I really struggle to see the downside of making the minimum, say, 400m instead of 500m.

I think the main problem here is that Strava is trying to make the segment matching to still work for road cycling activities that use Garmin smart recording. With the smart recording the data points can be a few seconds apart. When cycling at speed, 10-15 meters/sec is easily possible. With the smart recording that might lead to datapoints being 50-100 meters apart.

Because of the above consideration the radius for matching the segment start and finish is quite large. I remember reading somewhere that it is around 50-75 meters. Unfortunately it seems that the same radius applies to all segments regardless of the activity type. I've seen that in some running segments where someone does hill repeats and turns around at the top of the hill too early, and they still get a top position on the leaderboard even though they are clearly too far from the segment finish. When running uphill 50 meters is a long distance.

Now with the radius that large, if the segment is too short, you may see ridiculously wrong matchings of segments. For example, on a segment that is 300 meters long, someone, if they are extremely lucky or if they cheat and know what they are doing, may end up covering only half of the distance and still match the segment. And that has nothing to do with the GPS accuracy. That could be achieved with a perfectly accurate GPS just by entering and exiting the segment at the right points, for example, by turning around just on the edge of the matching radius.

So instead of fixing the problem above Strava increases the minimal segment distance limit. That still allows someone to match a shorter distance and get an unfairly shorter time, but now that error in the segment matching won't be as egregious. For example, they may end up matching the distance that is just 20% shorter instead of 50% shorter.

One solution that Strava should strongly consider is using interpolation. That should allow to narrow down the matching radius from 50-75 meters to something more reasonable like 10-20 meters. Even if someone's device records points every few seconds, with the interpolation that could be lowered down to 1 second and match positions that are much closer to the segment's true start and finish. That would allow to shorten the minimum segment length while still matching more accurate segment times.

Strava really need to consider that a number of MTB tracks in forest zones are shorter and even under the old 300m limit. We have several great tracks that are technical DH or climbs all under 300m which we could not make segments for previously. Sure make road segments longer but MTB need shorter segment lengths! Come on @Strava listen to your users and get this sorted. one rule for all is outdated thinking! Your app is fast being left behind and at risk of becoming irrelevant.

I'm mountain bike trail builder, and from my experience in my area, it is hard to make 500+ long trail. Also, when i finish trail, i dont ride it and than create segment. Since GPS frequency is 1Hz, I walk it slowly to create more accurate and more precise trail GPS track.  
I understand Strava to create limit, but for MTB 300meters should be minimum. 

Thanks

It looks like the minimum length for segments was changed which makes it impossible to add segments for a lot of popular mountain biking trails which are often between 300-500m.

I understand there's a challenge with short segments for downhill road cycling (where speed might make GPS tracks more inaccurate), but for mountain biking this really shouldn't be an issue. It looks like the minimum length was shorter at some point since there are a lot of existing segments that are shorter than 500m.

One possible solution would be to have different length limits based on the activity type - could allow shorter ones (ie. >=300 meters) for mountain biking and e-mountain biking. 

This discriminates against mountain bikers and shows that strava is definitely catering more to roadies which is super disappointing. MTBers deserve CR/KOM/QOMS too

It doesn't really matter Strava is dead now.  E-bikes have ruined it.   They don't seem to really care about e-bikes either.    Just like they don't care about segment length for MTBers.    My wife and I won't be renewing our subscriptions this year. 

I've come to the forum specifically to request shorter segments. I was just trying to create a 300m uphill sprint segment. I'm a sprinter and even super short 50m segments are important to track for me--as they are to most sprinters wanting to keep track of starts. Some of our races are only 200m long. We should be able to create short private segments, though public is also probably a desirable thing. As a short distance track sprinter, the 300 to 500 change might be a subscription deal breaker for me--500 is the longest sprint distance I train for...the shortening happened during a time when I was off the bike by Drs orders and I've just discovered the change as some segments I that were there in the past are missing--probably from the "cleanup". I'm very disappointed with Strava on discovering this change.

This new minimum length has nothing to do with "accuracy of timing" but it certainly does degrade riders' safety when they can't shorten an unsafe segment that ends right at an intersection.  Fwiw - modern GPS units can track speed over 100, 200 and certainly 300m very well.  No, the change likely has to do with the execs wanting to save money on infrastructure overhead required to track a lot of short segments.  I wish they'd just say so if that's the case instead of lying to their customers.  I came upon this post after trying to create a safer version of a favorite hill whose segment ends right at a busy intersection.  Often I sit two meters from the end of it waiting on the light and cars in front of me.  I tried to shorten it by ten meters and found out I can't make anything close to this segment anymore thanks to their unilateral change.  With recent price hikes and other unsavory corporate behavior recently, I'll certainly be on the lookout for Strava's competition.

As a mtbr myself I'm wondering where all these poor people live with only 300m long trails to ride.  That's sad.  Even here in backwater NC we have cities with MTB trails longer than that!  As for the idea making exceptions for MTB and ceding to "downhill" road segments being a challenge.  1.)  MTB trails are often obscured from the sky by trees and   2.) MTB trails are often much more convoluted, introducing more error in the track.  3.)  Sprinters rarely see anything close to 500m in the close of a race so we're screwed if we use Strava for performance tracking.  Rather than use this as another opportunity to segregate ourselves like newbs, lets just agree this decision is a huge fail on Strava's part.  There is nothing preventing Strava from recording segments under 500m other than pure stinginess.  By lengthening the segments minimums they have to maintain fewer segments.  It's a purely finance-driven decision.

i'm not certain that your premise is correct. On Garmin, yesterday, I created an uphill sprint segment that I calculated to be 482m long. Today, someone clocked that segment at 48.5mph. This is clearly a recording error. Two other people broke 40mph. If you look at those people's rides, most did not even break 30mph even going downhill. So, perhaps there is some merit to timing accuracy claim...i'm going to have to do some research.

Sad evolution. Some streets are 400 meters long where a 300 meter sprint is perfectly possible. Such as the street where I'm moving to later this year. Wanted to make a segment to honour it, sprinted all out, but I can't even create the full street as a segment anymore since it's too short. And yes, for off-road cycling it's even worse.

I hope the Strava board will turn this decision around. Sincerely.

Is there not a method by which GPS accuracy can be detected and then the information used to disqualify segment times for that ride?

@dswest - Are you sure it was a recording error and not just a case of someone not turning off their GPS after getting in the car and driving the segment?  Usually, when I see speeds in the 40-45mph range, it is simply because they had forgotten to turn off the GPS when they finished their ride and drove home.

Most of the earlier replies to this thread say it all. From an mtb perspective, many potential segments are short in length but not in time taken to complete due to the technicality and skill required to ride them. The 500m rule is crazy and only encourages new segment makers to artificially change the start/end points to meet the requirement. This devalues the segment. 

Yes, there is no road adjacent--it's a bike path cutting through the desert. I held the KOM until recently...i logged me at 50, I was only doing 27.8 (from a standing start) which is not bad for an old guy on a pretty good grade. I covered the distance in 21.4 seconds according to my Garmin which measured .30 miles...i think the length is the problem--I think it's more in the neighborhood of 250m. The new KOM is 21.3 seconds. It's frustrating but there is clearly some measurement variation that is causing problems...Strava may have cause to set min. length given the vast array of GPS devices reporting location. I'm not happy about it, but I'm a data scientist by trade and the data tells me something is off.

Presumably one could compare accuracy of place--does the GPS vary from the path within some tolerance, but it's very difficult to tell how accurate a particular GPS is without some kind of calibration. I suppose that if I had the time, and the data set, I could create a model that could detect with reasonable certainty if something was accurate (I'm a data scientist by trade) but, unfortunately, I have neither. What I do have is my own N of 1 data set which tells me mine is sometimes quite good and other times horrible (e.g. last week while riding the velodrome in LA when it put me in the LA river for a few laps...it also recorded my speed for my flying 200m at ~half of what it actually was!--there are official timings so the speed is known.